[clang] [llvm] Add support for Windows hot-patching (PR #138972)

[Hans Wennborg via cfe-commits]

zmodem wrote:

This is very interesting!

Initially I also assumed this was about Edit&Continue. As users may have the same idea, I'd suggest adding `DocBrief`s to the new Clang options, and a comment at the top of llvm/lib/CodeGen/WindowsHotPatch.cpp that explain in more detail what they do.

https://github.com/llvm/llvm-project/pull/138972